Conventional test systems often include a test head which provides an interface between a testing device and a device under test (DUT) and a prober which determines the test position of the DUT. When connecting a test head to a prober, it is generally accepted that the test head is connected in an upright position onto the top of the prober. In the space above a wafer, a connection ring is provided and attached such that it is supported by the prober. A probe card is connected to the bottom of the connection ring and includes a needle or so forth for probing the wafer.
The test head is coupled to a probe hinge, via an arm. Towards the top of the test head, a DUT board is set. By pivoting centrally around the probe hinge, a state of pressure is applied to the connection ring and contact is made between the test head and the prober. A plurality of pogo-pins are built into the connection ring and allow an exchange of signals between the DUT board and the probe card; and an electrically conductive pad pattern is provided on the DUT board where each pogo-pin makes contact with the probe card. In this way, a signal pathway is formed from the test head to the DUT board, to the connection ring, to the probe card, to the needle and, then, to a chip on the wafer.
The pogo pins are connecting terminals that hold a structure where the pins of a cylinder are supported by way of a spring. The connection is performed by applying the appropriate force to the conductive flat pad which is formed on a base. Such an arrangement provides a simple connection method for mechanically and simultaneously connecting a plurality of pins. This is especially useful for hinge coupled contacts that can be easily connected even though their center axis are tilted at the time of connection.
There is an increasing need for an ability to transmit test signals to a chip on a wafer at very high frequencies (high frequency bands) that reach up to 6 GHz. Such demand for performance cannot be accomplished by using pogo-pins. In the high frequency range, pogo-pins cause a large reflection loss and, realistically, their limit is about 1 GHz.
One possible approach to achieve transmission of high frequency signals of up to 6 GHz is to utilize a coaxial connector. A coaxial connector provides an inexpensive and simple snap-in type of SMB connection. The snap-in type connectors have a male connector and a female connector which are engaged by snapping in the direction of the central axis without rotating them along the cylindrical cross-section of the connectors. However, in reality, it is difficult to stably transmit a high frequency signal in the 6 GHz range using a coaxial connector. Another problem with coaxial connectors involves the absence of a mount construction that is capable of mechanically connecting a plurality of snap-in type coaxial connectors that are hinge coupled.
Other types of coaxial connectors such as a SMA, APC-3.5 or K can also be utilized to transmit high frequency signals in the 6 GHz range. Such connectors utilize screws to perform the connection. As a result, engaging the connector is mechanically cumbersome and time consuming as each screw must be manually secured, one at a time.
U.S. Pat. No. 5,558,541 (assigned to the common assignee of the present invention and incorporated herein by reference) discloses a blind mate connector, which is a snap-in type coaxial connector that has the ability to be mechanically connected and is interchangeable with the SMA connector. The blind mate connector does not have screw threading formed on the male connector. Instead, the screw threading is formed on the female connector such that a connection can be made by sliding the female connector into the male connector. The blind mate connector provides sufficient bandwidth to transmit high frequency signals of up to 6 GHz.
FIG. 1 illustrates the components of the blind mate connector and mount device, disclosed in the U.S. Pat. No. 5,558,541. In FIG. 1, a male connector 116 and a female connector 126 with mount components (an iris 144C, a spring 146 and a lip 148A) are shown. Female connector 126 is attached such that a spring 146 is inserted into a cylindrical component 144 of the test head by way of a collar 148. Female connector 126 engages male connector 116 when a fixture board 114 with male connector 116 is pressed thereon. As fixture board 114 is pressed, female connector 126 and male connector 116 are brought together with appropriate force by way of spring 146 which is compressed by iris 144C and lip 148A of collar 148. Spring 146 also has the effect of absorbing (i.e., adjusting to) the varying heights of each of the male connectors when a plurality of male connectors are attached to fixture board 114.
Although the prior art device shown in FIG. 1 may be utilized for inserting a male connector in the orthogonal direction into a female connector or vice-versa, it is not appropriate when using a prober and test head that are hinge coupled. That is to say, as the hinge is pivoted to connect the test head to the prober, the male connector and female connector move towards each other along an arc defined by the hinge mechanism. At the initial point of contact, both the central axis of the male connector and the female connector are positioned at a different angle (i.e., not aligned). Since the angle of the central axis cannot be changed or re-aligned, the only possible choice is to forcibly engage the connectors which results in abnormal friction and defective connection of the male and female connectors. With this type of coaxial connector for use with high frequency bands, the application of such force also results in a distortion of the structure, thus significantly reducing the electrical properties of the connectors.
Another possible remedy to the above-noted problems is to employ wider play between cylindrical component 144, female connector 126 and collar 148 and/or to tilt the central axis of the female connector. However, such a method requires excessive play which increases the error of the earlier position. Therefore, it can be assumed that a defective engagement will occur.
Accordingly, an objective of the present invention is to provide a floating mount apparatus for a coaxial connector which is suitable for use with hinge coupled devices.
It is a further object of the present invention to provide a coaxial connector and mount construction which allow the central axis of the coaxial connector to automatically adjust in the horizontal and vertical direction to provide a smooth, errorless engagement with another connector.
Another object of the present invention is to provide a floating mount apparatus of a coaxial connector adapted for use with high band signals and a prober and test head that are hinge coupled.